Rutheniun-Catalyzed Cycloisomerization of o-(Ethynyl)phenylalkenes to Diene Derivatives via Skeletal Rearrangement

• Published in: Journal of the American Chemical Society Vol. 126; no. 47; pp. 15560 - 15565
• Main Authors: Madhushaw, Reniguntala J, Lo, Ching-Yu, Hwang, Chun-Wei, Su, Ming-Der, Shen, Hung-Chin, Pal, Sitaram, Shaikh, Isak R, Liu, Rai-Shung
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 01.12.2004; Amer Chemical Soc
• Subjects: Chemistry; Chemistry, Multidisciplinary; Exact sciences and technology; Kinetics and mechanisms; Organic chemistry; Physical Sciences; Reactivity and mechanisms; Science & Technology; 3-BENZYL BUT-1-YNYL ETHERS; TRANSFORMATION; ENYNE METATHESIS; CYCLIZATIONS; AROMATIC ENYNES; PLATINUM; REORGANIZATION; 1-VINYLCYCLOALKENES; CARBENE COMPLEXES; TRANSITION-METALS; Catalytic reaction; Chemoselectivity; Catalyst selectivity; Transition metal Complexes; Complex catalyst; Experimental study; Organic solvent; Vinylic compound; Reaction mechanism; Ruthenium Complexes; Benzenic compound; Platinoid Complexes; Indene derivatives; Catalyst activity
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja045516n

Treatment of a series of 2‘,2‘-disubstituted (o-ethynyl)styrenes with TpRu(PPh3)(CH3CN)2PF6 (10 mol %) in benzene (80 °C, 12−18 h) efficiently gave 2-alkenyl-1H-indene derivatives. This catalytic reaction represents an atypical enyne cycloisomerization with skeletal rearrangement of starting enyne, where the CC bond is completely cleaved and inserted by the terminal alkynyl carbon. The reaction mechanism was elucidated by a series of deuterium and 13C labeling experiments, as well as by changing the substituents at the phenyl moieties. The mechanism is proposed to involve the following key steps:  5-endo-dig cyclization of ruthenium-vinylidene intermediate, a nonclassical ion formation, and the “methylenecyclopropane-trimethylenemethane” rearrangement.